(1) Field of the Invention
The present invention relates generally to sonar systems and, more particularly, to a close range sonar system for improved ambiguity resolution and increased heading/bearing resolution for underwater acoustic radiators.
(2) Description of the Prior Art
It is highly desirable to accurately and quickly determine the relative positions of acoustic radiators Timely and accurate information becomes important in certain situations.
Presently, the performance of some sonar systems has been determined to be less than optimal due to low signal-to-noise ratio (SNR) and noise problems. For instance, the flow of fluid creates considerable noise which hampers data collection/analysis Ambiguity resolution is therefore problematic without executing a ship maneuver. Towed arrays have been considered for such functions, but the performance of the towed array in the direction of the forward sector (i.e., end-fire) is perhaps even more hampered by ownship noise.
Various patents have addressed related issues but do not address the present problems.
U.S. Pat. No. 5,142,505, issued Aug. 25, 1992, to Francois Peynaud, discloses a sonar for avoiding sub-surface underwater objects, for a surface vessel, having its directivity in elevation optimized to observe the surface and its surface reverberation reduced to the minimum. It consists in using an acoustic antenna having two columns of n transducers, the first column insonifying, at transmission, an elevation sector corresponding to the close encounter-risk zone and forming channels at reception, in the insonified elevation sector, the width of the channels being all the finer as the desired precision of the measurement of the position in elevation is high. The second column is necessary for the localization in relative bearing. The disclosure can be applied to the precise localization in elevation of objects located in the path of a vessel.
U.S. Pat. No. 5,303,204, issued Apr. 12, 1994, to Shalom Wertsberger, discloses a device to warn a ship crew of submerged objects in their immediate vicinity, combined with alarm and logging facilities. The device is composed of one or more sonic or ultra sonic transducers placed aboard the ship, with coverage arranged so as to give surrounding “envelope” to the sides and to the area ahead of the vessel, as well as some predetermined downward looking angle. The transducer or transducers are connected to an electronic distance measuring device that will measure distance to possible obstacles, similar to conventional sonar techniques. The measurements in each direction are compared by an electronic processor against a table of minimum distances, and if the distance falls below the predetermined value for a given direction, an alarm is activated. In addition, all alarms, cancellations of alarms, activation and deactivation of the system are logged automatically with an identification of the operator.
U.S. Pat. No. 5,400,300, issued Mar. 21, 1995, to Bick et al., discloses a system for providing advance warning of underwater navigation hazards that threaten safe ship passage. The system includes a sonar transmitter/receiver adapted for mounting on the ship in a forward looking direction. A processor, in response to sonar returns produced by the sonar transmitter/receiver, produces a sonar produced slope profile of a region of the sea bottom in front of the path of the vessel. A memory stores a slope profile of the region of the sea bottom in front of the vessel, such profile being developed from charted depth data. The stored charted depth data developed slope profile is compared with the sonar return produced slope profile to determine whether the sonar produced slope profile and the charted depth data slope profile are consistent with each other. If the sonar return produced slope profile in a region of the sea bottom is greater that a predetermined threshold level (selected to identify a potential forward undersea hazard) and the charted depth data generated profile of such region does not indicate this potential hazard, an anomaly is identified and a signal indicating such anomaly is produced.
U.S. Pat. No. 5,708,626, issued Jan. 13, 1998, to J. Dana Hrubes, discloses a system for determining the velocity and trajectory of an underwater vehicle which comprises a data acquisition processor coupled to a plurality of sensors providing depth, heading, pitch and yaw data for the underwater vehicle. The acquisition processor collects data from the sensors, correlates and assembles the collected data into batches and processes the batches to determine vehicle velocity and trajectory of the vehicle relative to an earth-fixed coordinate system.
U.S. Pat. No. 5,969,665, issued Oct. 19, 1999, to Aleksandr L. Yufa, discloses a method and apparatus which provide a control of the vessel maneuvering by a determination and displaying of the dangerous relative course zones, wherein the end of the vessel speed-vector should not be located for the object evasion tactic maneuvering and/or close encounter avoidance maneuvering and should be located for the object pursuit and/or interception tactic maneuvering. The apparatus comprises an object disposition evaluator, a control system, a dangerous criteria setting system, an initial data processor, at least one display and a dangerous relative course zone determiner, including an interface-signal distributor, a logic processor and signal distributor and a data processing system, comprising a trigonometric function processor, a summator, a multiplier-divider and a data processor. The dangerous relative course zones are displayed on at least one indicator, providing the operator with the possibility to evaluate the danger approach situation and instantly select the anti-collision maneuver for collision preventive maneuvering and/or select an optimal maneuver for the assigned vessel tactic maneuvering execution.
U.S. Pat. No. 6,249,241, issued Jun. 19, 2001, to Jordan et al., discloses a marine Vessel Traffic System (VTS) that is an improved radar harbor surveillance sensor, computer and display system that monitors marine harbor traffic, that provides advisories to vessels in areas selected by the system operators, and that provides the operators of the system with an early warning of unacceptable traffic conflicts in the confined waterways of the harbor. The VTS collects harbor traffic information from multiple remote sensor collection sites around the harbor and integrates, records, merges and presents the remote site data onto a single operator display, selected from a plurality of operator displays. VTS provides quick accurate computer generated graphic display of the harbor traffic, possible surface and subsurface conflicts, and key vessel identification information and the VTS documents incidents and traffic conditions for the Coast Guard or other waterway authorities.
It would be desirable to improve sonar performance in the forward sector and to provide a rapid resolution of port/starboard ambiguity resolution. These functions are required if our submarines are to safely and effectively maneuver in close encounter situations. The solutions to the above-described problems have been long sought without success. Consequently, those skilled in the art will appreciate the present invention that addresses the above and other problems.